1. Field of the Invention
The present invention relates to a playback apparatus adapted to play back stream data and method of controlling a playback operation of a playback apparatus, and more particularly, to a playback apparatus and a playback control method of receiving stream data transmitted from a server connected to the playback apparatus via a network and playing back the received stream data.
2. Description of the Related Art
Audio/video contents are widely used in the form of digital data, and various apparatus for easily recording/playing digital data of audio/video contents are available. Great advances in network technology have been made, and thus it has become possible to easily build a home network system using a LAN (Local Area Network) or a wireless LAN.
Thus, it is desirable to provide a technique to easily transmit digital contents between devices in a home network system. In view of the above, efforts of establishing standards for procedures of connection between devices and control of contents are under way. One of such standards is UPnP (Universal Plug & Play) proposed by Microsoft Co., Ltd. of USA. The DLNA (Digital Living Network Alliance) guideline has been established based on the UPnP standard, and efforts of developing various devices according to the DLNA guideline are under way.
In the UPnP standard, UPnP devices are classified into three groups: media servers for providing contents, control points serving as control terminal devices, and media renderers serving as playback apparatuses. Note that the function of a control point may be implemented in a device serving as a media server or in a device serving as a media renderer.
A procedure (protocol) of communication between devices is defined in the UPnP standard, and it is possible to search for a UPnP device on a network and control an operation such as a playback operation of the UPnP device in accordance with the defined communication procedure. More specifically, for example, the control procedure allows a media renderer not only to transmit/receive content data from/to a media server but also to transmit content data to other media renderers (see, for example, Japanese Unexamined Patent Application Publication No. 2005-250867(paragraphs to 0097], FIG. 7)).
To play back audio/video stream data, it is necessary to control the storage of data such that as much stream data as required to properly perform a playback operation always exists in an input buffer of a decoder. Therefore, to continuously play back stream data of a plurality of contents, it is necessary to acquire stream data of a next content and start storing the acquired stream data into the input buffer of the decoder before playback of a previous content is ended.
One method of managing the input buffer of the decoder is to estimate playback times of respective input data which may be different in format, and control reading of data into the input buffer on the basis of the playback time for data existing in the input buffer thereby achieving playback of a plurality of data which may be different in format (see, for example, Japanese Unexamined Patent Application Publication No. 2005-182970 (paragraphs [0096] to [0116], FIG. 7)).